net: don't global ICMP rate limit packets originating from loopback

netoptimizer · davem330 · commit 849a44de9163 · 2017-06-14T15:33:58.000-04:00
Florian Weimer seems to have a glibc test-case which requires that loopback interfaces does not get ICMP ratelimited. This was broken by commit c0303ef ("net: reduce cycles spend on ICMP replies that gets rate limited"). An ICMP response will usually be routed back-out the same incoming interface. Thus, take advantage of this and skip global ICMP ratelimit when the incoming device is loopback. In the unlikely event that the outgoing it not loopback, due to strange routing policy rules, ICMP rate limiting still works via peer ratelimiting via icmpv4_xrlim_allow(). Thus, we should still comply with RFC1812 (section 4.3.2.8 "Rate Limiting"). This seems to fix the reproducer given by Florian. While still avoiding to perform expensive and unneeded outgoing route lookup for rate limited packets (in the non-loopback case). Fixes: c0303ef ("net: reduce cycles spend on ICMP replies that gets rate limited") Reported-by: Florian Weimer <fweimer@redhat.com> Reported-by: "H.J. Lu" <hjl.tools@gmail.com> Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com> Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/icmp.c b/net/ipv4/icmp.c
@@ -657,8 +657,12 @@ void icmp_send(struct sk_buff *skb_in, int type, int code, __be32 info)
 	/* Needed by both icmp_global_allow and icmp_xmit_lock */
 	local_bh_disable();
 
-	/* Check global sysctl_icmp_msgs_per_sec ratelimit */
-	if (!icmpv4_global_allow(net, type, code))
+	/* Check global sysctl_icmp_msgs_per_sec ratelimit, unless
+	 * incoming dev is loopback.  If outgoing dev change to not be
+	 * loopback, then peer ratelimit still work (in icmpv4_xrlim_allow)
+	 */
+	if (!(skb_in->dev && (skb_in->dev->flags&IFF_LOOPBACK)) &&
+	      !icmpv4_global_allow(net, type, code))
 		goto out_bh_enable;
 
 	sk = icmp_xmit_lock(net);
diff --git a/net/ipv6/icmp.c b/net/ipv6/icmp.c
@@ -491,7 +491,7 @@ static void icmp6_send(struct sk_buff *skb, u8 type, u8 code, __u32 info,
 	local_bh_disable();
 
 	/* Check global sysctl_icmp_msgs_per_sec ratelimit */
-	if (!icmpv6_global_allow(type))
+	if (!(skb->dev->flags&IFF_LOOPBACK) && !icmpv6_global_allow(type))
 		goto out_bh_enable;
 
 	mip6_addr_swap(skb);
